Re: [PATCH 00/16] treewide: prefer __section from compiler_attributes.h

On Mon, Aug 12, 2019 at 11:53 PM Nick Desaulniers
[off-list ref] wrote:

GCC unescapes escaped string section names while Clang does not. Because
__section uses the `#` stringification operator for the section name, it
doesn't need to be escaped.

This fixes an Oops observed in distro's that use systemd and not
net.core.bpf_jit_enable=1, when their kernels are compiled with Clang.

Instead, we should:
1. Prefer __section(.section_name_no_quotes).
2. Only use __attribute__((__section(".section"))) when creating the
section name via C preprocessor (see the definition of __define_initcall
in arch/um/include/shared/init.h).

This antipattern was found with:
$ grep -e __section\(\" -e __section__\(\" -r

See the discussions in:
https://bugs.llvm.org/show_bug.cgi?id=42950
https://marc.info/?l=linux-netdev&m=156412960619946&w=2

Nick Desaulniers (16):
  s390/boot: fix section name escaping
  arc: prefer __section from compiler_attributes.h
  parisc: prefer __section from compiler_attributes.h
  um: prefer __section from compiler_attributes.h
  sh: prefer __section from compiler_attributes.h
  ia64: prefer __section from compiler_attributes.h
  arm: prefer __section from compiler_attributes.h
  mips: prefer __section from compiler_attributes.h
  sparc: prefer __section from compiler_attributes.h
  powerpc: prefer __section and __printf from compiler_attributes.h
  x86: prefer __section from compiler_attributes.h
  arm64: prefer __section from compiler_attributes.h
  include/asm-generic: prefer __section from compiler_attributes.h
  include/linux: prefer __section from compiler_attributes.h
  include/linux/compiler.h: remove unused KENTRY macro
  compiler_attributes.h: add note about __section

Hi Nick,

thanks for this patchset and the nice section names cleanup and simplification.

I have tested 5 relevant patches for my x86-64 Debian/buster system.

Patchset "for-5.3/x86-section-name-escaping" (5 patches):

compiler_attributes.h: add note about __section
include/linux/compiler.h: remove unused KENTRY macro
include/linux: prefer __section from compiler_attributes.h
include/asm-generic: prefer __section from compiler_attributes.h
x86: prefer __section from compiler_attributes.h

Toolchain: LLVM/Clang compiler and LLD linker version 9.0.0-rc2 (from
Debian/experimental)

I can boot on bare metal.

$ cat /proc/version
Linux version 5.3.0-rc5-1-amd64-cbl-asmgoto
(sedat.dilek@gmail.com@iniza) (clang version 9.0.0-+rc2-1~exp1
(tags/RELEASE_900/rc2)) #1~buster+dileks1 SMP 2019-08-19

I have sent by Tested-by to the single patches.

Have a nice day,
- Sedat -

 arch/arc/include/asm/linkage.h        |  8 +++----
 arch/arc/include/asm/mach_desc.h      |  3 +--
 arch/arm/include/asm/cache.h          |  2 +-
 arch/arm/include/asm/mach/arch.h      |  4 ++--
 arch/arm/include/asm/setup.h          |  2 +-
 arch/arm64/include/asm/cache.h        |  2 +-
 arch/arm64/kernel/smp_spin_table.c    |  2 +-
 arch/ia64/include/asm/cache.h         |  2 +-
 arch/mips/include/asm/cache.h         |  2 +-
 arch/parisc/include/asm/cache.h       |  2 +-
 arch/parisc/include/asm/ldcw.h        |  2 +-
 arch/powerpc/boot/main.c              |  3 +--
 arch/powerpc/boot/ps3.c               |  6 ++----
 arch/powerpc/include/asm/cache.h      |  2 +-
 arch/powerpc/kernel/btext.c           |  2 +-
 arch/s390/boot/startup.c              |  2 +-
 arch/sh/include/asm/cache.h           |  2 +-
 arch/sparc/include/asm/cache.h        |  2 +-
 arch/sparc/kernel/btext.c             |  2 +-
 arch/um/kernel/um_arch.c              |  6 +++---
 arch/x86/include/asm/cache.h          |  2 +-
 arch/x86/include/asm/intel-mid.h      |  2 +-
 arch/x86/include/asm/iommu_table.h    |  5 ++---
 arch/x86/include/asm/irqflags.h       |  2 +-
 arch/x86/include/asm/mem_encrypt.h    |  2 +-
 arch/x86/kernel/cpu/cpu.h             |  3 +--
 include/asm-generic/error-injection.h |  2 +-
 include/asm-generic/kprobes.h         |  5 ++---
 include/linux/cache.h                 |  6 +++---
 include/linux/compiler.h              | 31 ++++-----------------------
 include/linux/compiler_attributes.h   | 10 +++++++++
 include/linux/cpu.h                   |  2 +-
 include/linux/export.h                |  2 +-
 include/linux/init_task.h             |  4 ++--
 include/linux/interrupt.h             |  5 ++---
 include/linux/sched/debug.h           |  2 +-
 include/linux/srcutree.h              |  2 +-
 37 files changed, 62 insertions(+), 83 deletions(-)

--
2.23.0.rc1.153.gdeed80330f-goog